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<br />(;02'102 <br /> <br />fishes pose a threat to the Colorado River fauna. Finally, institutional recognition of <br />and support for such a plan.is urgently needed. <br /> <br />A workshop was held in Boulder, CO on Nov 30 and Dee 1, 1995 to seek <br />answers to four basic questions concerning the kinds of solutions available for the <br />UCRB: (1) In what geographic areas would control measures have the greatest <br />benefit? (2) Which life history stages of the endangered fishes are most susceptible to <br />negative interactions with nonnative fishes? (3) Which nonnative species pose the <br />most serious threats? (4) Which control methods will be most effective? The workshop <br />tapped the collective expertise of scientists and managers who were familiar with <br />problems in the upper basin, and who represented perspectives from the various <br />geographical areas and governmental agencies within the basin. Participants identified <br />priority geographic areas for recovery of the native fishes in the Green River below <br />Echo Park, the lower Yampa, and the Colorado above the Green River confluence. <br />Larval and juvenile stages of all natives fishes were considered most susceptible to <br />predation by a wide range of introduced predators. The channel catfish was <br />considered the greatest threat, but green sunfish, fathead minnow, red shiner and <br />others also were recognized as threats. <br /> <br />Workshop participants also proposed a number of control scenarios based <br />solely on technical merits. The scenarios discussed included three basic themes: 1) <br />prevent nonnative fishes from entering the system, 2) remove non natives from the main <br />channel, and 3) exclude non natives from interactions with larval and juvenile native <br />fishes. Installation of effective escapement controls on major reservoirs such as <br />Elkhead, Kenney, Highline, and Starvation, and on other known source areas like <br />Browns Park and Stewart Lake waterfowl management areas in Utah could reduce the <br />supply of nonnative fishes such as common carp, northern pike, smallmouth bass, and <br />black crappie. For the ponds in the floodplain, chemical techniques could be applied to <br />eliminate nonnatives. Mechanical techniques such as trapping or electrofishing could <br />be applied in critical habitat (e.g., lower Yampa, lower Green, and the Colorado above <br />the Green) for the removal of larger nonnatives such as channel catfish, carp, and <br />centrarchids. Flow management, especially in high gradient areas, has some potential <br />for reducing populations of small cyprinids and the centrarchids. Active management <br />of the inundation cycle for backwaters and floodplain ponds could be a principal <br />mechanism for reducing negative interactions (i.e., predation) on larval nonnative <br />fishes. Barriers, weirs, and other exclusion measures could be installed in certain high <br />priority areas. <br /> <br />Scenarios developed by workshop participants form a large component of the <br />technical basis of the proposed strategic plan, which will guide control efforts. The plan <br />reaches beyond workshop scenarios because it must integrate control efforts in a <br />basinwide context, and it ventures beyond a strictly technical framework because it <br />acknowledges potential sociopolitical conflicts and major non-technical constraints. <br /> <br />v <br />